Various types of magnetic technology utilize magnetic elements for storing or reading data. For example, in conventional MRAM technology, the conventional magnetic element used is a spin tunneling junction. The spin tunneling junction includes a ferromagnetic pinned layer having a magnetization that is typically pinned by an antiferromagnetic (“AFM”) layer. The spin tunneling junction also includes a ferromagnetic free layer separated from the pinned layer by an insulating barrier layer. The barrier layer is sufficiently thin to allow tunneling of charge carriers between the pinned layer and the free layer. Similarly, in conventional hard disk magnetic recording technology, the magnetic elements for magnetoresistive read heads include conventional magnetic elements, such as a spin valves. Spin valves include a ferromagnetic pinned layer having a magnetization that is typically pinned by an AFM layer. The spin valve also includes a ferromagnetic free layer separated from the pinned layer by a conductive, nonmagnetic spacer layer, such as Cu. The ferromagnetic pinned and free layers of the spin tunneling junction and spin valve may also by synthetic or composed of ferrimagnetic materials.
FIG. 1 depicts a high-level flow chart depicting of a conventional method 10 for forming a magnetic element, such as the spin valve and spin tunneling junction used in conventional MRAM and conventional magnetic recording technology. For clarity, only some steps in the conventional method 10 are described. For example, other structures such as contacts are not described or depicted. FIGS. 2A-2C depict the conventional magnetic element 50 during fabrication. Referring to FIGS. 1 and 2A-2C, the layers for the conventional magnetic element 50 are deposited, via step 12. For example, step 12 may include depositing a seed layer, an AFM layer, a pinned layer, a nonmagnetic spacer layer and a free layer. A bilayer photoresist structure is provided on the layers for the conventional magnetic element 50, via step 14.
FIG. 2A depicts the conventional magnetic element 50 during formation on a substrate 52. The conventional magnetic element 50 includes magnetic element layers 54. The magnetic element layers 54 might include an AFM layer, a pinned layer, a barrier layer or nonmagnetic spacer layer, and a free layer that are not explicitly shown. The magnetic element layers 54 might include other layers, such as capping layers, or other magnetic layers for example for dual spin valves or dual spin tunneling junctions. Also shown in the bilayer photoresist structure 56. The bilayer photoresist structure 56 includes a lower layer 58 and an upper layer 60 that extends past the edges of the lower layer 58.
Using the bilayer photoresist structure 56 as a mask, the magnetic element layers 54 are ion milled, via step 16. Step 16 thus defines the magnetic element 50. FIG. 2B depicts the magnetic element 50 after step 16 has been completed. Structures which are analogous to those depicted in FIG. 2A, such as the substrate 52, are labeled similarly. Thus, a portion of the magnetic layers 54′ has been removed, leaving the magnetic element 50.
An insulator may then be provided, via step 18. During deposition of the insulator, the bilayer photoresist structure 56 masks the underlying magnetic element 50 from the insulator. The bilayer photoresist structure 56 is removed, via step 20. Processing of the magnetic element 50 is then completed, via step 22. FIG. 2C depicts the conventional magnetic element 50 after further processing. Consequently, the insulator 62 has been provided. Thus, the conventional method 10 can provide a conventional magnetic element 50.
Although the conventional method 10 and conventional magnetic element 50 function, one of ordinary skill in the art will readily recognize that the current trend in various types of magnetic technology is toward smaller magnetic elements. For example, in conventional MRAM technology, the trend is toward higher density memories and, therefore, smaller sizes of the magnetic element. Similarly, the trend in conventional hard disk magnetic recording is toward a higher density recording media having smaller bit sizes. Thus, the magnetic elements for read and write heads used in hard disk drives are also more compact. Consequently, the width, w depicted in FIGS. 2B and 2C, is desired to be smaller. In particular, for many applications, the width of the magnetic element 50 is desired to be 0.15 micron or less.
Although the conventional method 10 can be used to fabricate magnetic elements, one of ordinary skill in the art will readily recognize that the use of the conventional method 10 may not reliably fabricate smaller magnetic elements. Using the method 10, 0.12×0.22 micron structures may be fabricated from 0.248 micro photolithography. However, magnetic elements having a width of less than or equal to 0.15 micron may not be reliably fabricated using the conventional method 10. During fabrication, the bilayer photoresist structure 56 may not adequately mask the underlying magnetic element layers 54 at smaller widths. The portion of the upper layer 60 that overhangs the edges of the lower layer 58 may break off at lower widths. Moreover, the lower layer 58 may detach from the underlying magnetic element layers 54. Consequently, the magnetic element 50 does not have the desired size. In addition, the insulator 60 and other features fabricated on the magnetic element, such as contacts, will not be in the appropriate places. Thus, failures of the magnetic elements 50, as well as other structures, can result.
Accordingly, what is needed is a system and method for reliably fabricating magnetic elements having smaller widths. The present invention addresses such a need.